A prior dishwasher is disclosed in U.S. Pat. No. 4,172,463. In the '463 dishwasher, a chamber for receiving dishes to be washed is provided within an outer case. Water is collected in a liquid container at a bottom portion of the chamber. Water is sprayed onto the dishes by a pump. Sprayed water is returned to the liquid container to be recycled. A heater is located in the liquid container. During washing the heater heats the water and during drying the heater heats air to dry the dishes efficiently.
In this type of dishwasher, however, when water is circulated by the pump, a water level in the liquid container may become lower than the position of the heater. As a result, water in the liquid container is not heated efficiently by the heater, so that much time is required to heat water to a predetermined temperature suitable for washing the dishes. Therefore, it takes much time to wash the dishes.
Another known dishwasher includes a sensor for detecting the temperature of the water. Until the temperature of the water reaches a predetermined temperature, the pump is stopped so that much time is not required to heat the water. However, this causes a different problem.
Since the water is not sprayed to the dishes for a while from the beginning of the washing operation, refuse on the dishes becomes dried and tends to stick to dish surfaces. Therefore, it is not easy to remove the refuse from the dishes.